1. Field of the Invention
This invention relates to an optical buffer device that is capable of holding signal light.
2. Description of the Related Art
Each node that configures an optical communication system network includes a router that performs line switching for transmitting signal light with respect to an intended node.
At present, each node that is used in an optical communication system network converts an optical signal that has been-received into an electrical signal once and performs processing that is necessary for line switching. Thereafter, each node converts the electrical signal into an optical signal and transmits that optical signal to another node.
Research on so-called optical routers that perform this line switching processing in the state of the optical signal without converting the optical signal into an electrical signal has heretofore been conducted. In technologies that are used in optical routers, an optical switch that spatially switches the traveling direction of light is relatively easily realizable. In contrast, other than an optical fiber that simply delays light, a good optical fiber that holds signal light is not known. For example, an optical bistable element is usable as an optical buffer device, but an optical bistable element cannot store anything other than intensity of the physical information that light holds.
Recently, as a technology that is applicable to an optical buffer device, a technology that stops light by controlling the group velocity of light is gathering attention. In this control of the group velocity of light, control that uses photonic crystal and a resonator (e.g., see Japanese Patent Application Publication (JP-A) No. 2006-234964 and Document 1 listed below) and control that uses an electromagnetically induced transparency (EIT) material that utilizes atomic level (e.g., see Document 2 listed below) are known.
Document 1: M. F. Yanik et al., “Stopping Light in a Waveguide with an All-Optical Analog of Electromagnetically Induced Transparency”, Phys. Rev. Lett. Vol. 93, (2004) 233903
Document 2: “Dark-State Polaritons in Electromagnetically Induced Transparency” (M. Fleischhauer and M. D. Lukin, Phys. Rev. Lett. Vol. 84 (2000) pp 5094-5097)
However, in regard to the aforementioned technology that stops light by controlling the group velocity of light, heretofore there has mainly been theoretical research. Consequently, virtually no proposals have been made in regard to a specific configuration that uses this technology in optical communication.